A goal of pharmaceutics is to efficiently deliver a therapeutic drug to the site of action. Over the years, methods have been developed to achieve this goal. We describe here a unique drug delivery system which at room temperature and lower has the property of a liquid but when administered topically to the skin becomes a semi solid or gel when warmed by the body. The advantages of such a system for application to the skin are (1) the drug delivery system can be applied to tender, sensitive skin by a pour on application with no need to rub the area to obtain coverage, and (2) a liquid will flow into crevices and pores providing intimate contact with the skin.
When gelled, the drug delivery system remains in place with a flexible covering to the area of skin on which it is applied. Drugs are delivered to the skin from the gel but these drugs can also be removed by running cool water over the area. Such a drug delivery system will have application especially for burn patients where application and removal of drugs required gentle techniques because of the tender surface to which application is to be made.
A drug delivery system has been described in U.S. Pat. No. 4,188,373 using "Pluronic.RTM." polyols as the thermally gelling polymer. In this system the concentration of polymer is adjusted to give the desired sol-gel transition temperature, that is the lower the concentration of polymer the higher is the sol-gel transition temperature. However, with the commercially available "Pluronic.RTM." polymers the ability to obtain a gel of the desired rigidity is limited while maintaining the desired sol-gel transition temperature at physiologically useful temperature ranges near 26.degree.-35.degree. C.
Similarly, a Canadian Pat. No. 1,072,413 which relates to "Pluronic.RTM." polyols (poloxamer polyols) with gelling temperatures lower than room temperature uses additives to modify the gelling characteristics. Also, in this Canadian patent "Tetronic.RTM." polymers (poloxamine polyols) are used as additive agents rather than the primary polymeric agent as in the instant case.